While there are a number of commercially available mild to moderate analgesic agents, the search for alternative analgesic agents has continued because of the problems attendant with current therapy.
Aspirin and related salicylates are considered to be non-narcotic analgesic agents useful for relieving mild to moderate pain, in addition to their anti-inflammatory and anti-pyretic properties. However, the ingestion of salicylic acid or related salycilates may result in epigastric distress, nausea and vomiting. This widely used class of non-narcotic analgesic agents may also cause gastric ulceration and even hemorrhage both in experimental animals and man. Exacerbation of peptic ulcer symptoms and erosive gastritis have all been reported in patients on high dose therapy, i.e., arthritis patients. Aspirin is also one of the most common causes of drug poisoning in young children and has a potential of serious toxicity if used improperly.
Acetominophen is also considered to be a non-narcotic analgesic agent useful in treating pain associated with simple headache, common muscular aches, etc. While acetominophin is particularly useful for patients who cannot take aspirin, i.e. ulcer patients, its use in contraindicated in individuals who have exhibited a sensitivity to it.
In addition to their drawbacks in view of their potential side effects, the mild, non-narcotic analgesic agents are not sufficiently potent to relieve the severe pain associated with surgery, cancer and the like.
Unfortunately, the potent analgesic agents capable of relieving such severe pain are also narcotic agents and their use entails the risk of producing physical or psychological dependence.
One moderate analgesic agent which has enjoyed great commercial success for a number of years, .alpha.-d-propoxyphene hydrochloride (Darvon.RTM., Eli Lilly and Co., Indianapolis, Ind.) has been widely used to relieve pain associated with dental extractions, afterbirth pain, and some post-operative pain. This widely used analgesic agent has been reported to be ineffective in relieving many types of pain, and recently, reports of serious side effects and deaths have created a need for alternative, moderate analgesic agents. The present invention provides such agents.